I recently got my paper accepted by a "look-descent" conference (indexed by ACM, a leading association in CS). Now, I am considering to withdraw the paper for some considerations, yet, need to know first if that would be fair?

The problem is that i didn't got individual reviews but only a summary from the PC. The review summary looks general and doesn't make me feel
my paper had been seriously reviewed by a peer.
When I asked for review details, which should be available on the submission platform, the PC said they would be available after the registration. What
is weird also is that the registration is due after one week of acceptance notification only, and the paper will automatically be rejected if not registered by the deadline. The registration fee is expensive (more than twice) compared to what is usual in my home country (the conference is in the same country).

NB: I made sure the conference CFP is not fake!

Is it fair to withdraw the paper and what should I write to
notify the PC?

Since conferences websites doesn't tell that,
it would be beneficial to know in which cases one can
withdraw an accepted paper?

One could argue that you haven't made a commitment yet, but I'm not sure. It is also very field-dependent and therefore I don't really feel competent to answer. (In my field, conferences are not a publication venue and low-tier workshops are not really selective, so withdrawing is not a big deal. In CS, where getting into a conference is more difficult, you effectively take someone else's position* and the ethical implications may well be different.) If you don't get an answer, I suggest to rephrase your question and elaborate on the fairness/commitment issue.
– henningJun 23 '15 at 15:37

I have never heard of the practice of withholding reviews until registration. The reviewers work for free, I do not see why the conference should be entitled to keep their contribution from you.

On the other hand, about the registration fees, if that's something you knew beforehand, I do not think it's an appropriate argument to make that they are too high.

Bottom line: assuming you were aware of the fees beforehand, that's not a good point to make for withdrawing. However, withdrawing as reaction to the practice of withholding the reviews until registration, is. However, ensure that, if that's what you decide do, this is not a conference you are likely to ever return to.

Whatever you decide, it is the right thing to inform the organisers about the decision.

Registration fees are not always announced with the call for papers. And even then, I was once (almost) in a situation where my circumstances suddenly changed: my ex supervisor promised to finance my attending and presenting a joint paper as I was starting my postdoc elsewhere, and then promptly forgot that when it was accepted, trying to convince me I should pay from my own pocket. He suddenly changed his mind when I started informing coauthors that I might need to withdraw the paper as I can not finance attending.
– penelopeJul 10 at 9:26

@penelope If they are not announced, then I would consider a withdrawal legitimate, once it is clear they are too high.
– Captain EmacsJul 11 at 2:56